1. Field of the Invention
The present invention relates to a storage control device and a storage control device path switching method.
2. Description of the Related Art
In a variety of organizations such as government, public offices, local government, enterprise, and education and the like, data is managed using comparatively large-scale storage control devices for the handling of large volumes of various types of data. These storage control devices comprise storage areas having redundancy through the use of redundant information (RAID: Redundant Array of Independent Disks), and store data in the storage areas (Japanese Patent Application Laid-open No. 2003-108315). In the conventional technology described in this document, by switching access paths from the host in a stepped manner from an old storage control device to a new storage control device, data can be migrated between devices without halting access from the host.
Ease of access to data is required, and good availability (reliability), are both required of storage control devices in order to manage large amounts of data. Thus, by employing a redundant storage structure, duplication of access paths to the storage device, and duplication of the controllers, realization of good availability is possible.
However, even if access paths and controllers are duplicated, unless control signals connecting the controllers are duplicated, appropriate response will not be possible in some cases. For example, if a fault occurs in a control signal line connecting the controllers, the appropriate response to the fault in the control signal line may not be possible. However, if duplication is extended to the control signal lines, the number of control signal lines is doubled, complicating the structure of electrical connections between the controllers, and inviting an increase in size of the device.
In particular, if a fault occurs in the control signal for inducing switching of the storage device access path from the primary path to the alternate path, the path may be switched before preparations are completed for switching the controller to be the switching source.